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91.
The spectroscopic observations of comet C/2009 R1 (McNaught) were carried out with the 2 m Zeiss-RCC Telescope of Pik Terskol Observatory operated by the International Center for Astronomical and Medico-Ecological Research (Ukraine, Russia). The Multi Mode Cassegrain spectrometer was used to obtain spectra of moderate spectral resolving power with a wavelength coverage from 4140 to 5240 Å. The spectrum is characterized by the extremely low continuum level and strong molecular features. 192 emission lines of C2, CN, CH, NH2, CO+, and CH+ have been identified by the comparison of the observed and theoretical spectra of the molecules. The ratios of the gas production rates of Q(C2)/Q(CN)=1.32, Q(CH)/Q(CN)=0.49, and Q(NH2)/Q(CN)=0.81 were derived using a Haser model. 相似文献
92.
Fernando Unrein Inés O’Farrell Irina Izaguirre Rodrigo Sinistro María dos Santos Afonso Guillermo Tell 《Aquatic Sciences - Research Across Boundaries》2010,72(2):179-190
Phosphorus has been traditionally regarded as the controlling nutrient for phytoplankton growth, however, N-limitation is
likely to occur in several environments. For example, nitrogen is considered the main nutrient limiting phytoplankton in floodplain
lakes of the Paraná River basin. However, N2-fixing heterocystous cyanobacteria (N2-cyano) are usually absent in these water bodies. The low pH values frequently found may limit the development of these algae.
We hypothesise that long-term lake isolation allows conspicuous phytoplankton growth during summer, resulting in high photosynthetic
rates and pH. This scenario combined with low DIN (dissolved inorganic nitrogen) would favour the development of N2-cyano. Phytoplankton composition was studied during 16 months in a vegetated and isolated floodplain lake in the Paraná basin.
Additionally, pH was artificially increased in in situ mesocosms to test effects on phytoplankton structure. Lake phytoplankton
was dominated by flagellates (cryptophytes and euglenophytes) and small coccoid algae (chlorophytes and colonial cyanobacteria).
Algal biomass was highest during warm periods. Although pH increased up to 8.8 during the second summer period, N2-cyano remained rare, most likely because of the high DIN concentration recorded. The alkalophilic diatom Cyclotella meneghiniana dominated and was positively correlated with pH. Conversely, PO4= concentrations in the mesocosm experiment were high and DIN remained relatively low. pH enhancement in the treated mesocosms
(avg. pH = 8.2) promoted the development of N2-cyano (Anabaena spp.) and C. meneghiniana, which after 1 month of incubation accounted together for 50% of the biomass in contrast to less than 1.6% in control containers.
Our results support the hypothesis that during the warm season and under low DIN concentration, high pH favours N2-cyano growth in these lakes. We provide new evidence supporting the idea that even under optimal nutrient conditions, N2-cyano do not thrive unless other requirements are satisfied. 相似文献
93.
Irina N. Belskaya Anny-Chantal Levasseur-Regourd Yuriy S. Efimov Edith Hadamcik 《Icarus》2009,199(1):97-105
New UBVRI polarimetric observations of ten asteroids, including space mission targets 1 Ceres and 21 Lutetia, are presented. These observations were obtained with the 1.25-m telescope of the Crimean Astrophysical Observatory and have been used to study the wavelength dependence of polarization for a sample of asteroids belonging to the M and low albedo classes. A more general analysis including also a larger data set of UBVRI polarimetric observations available in the literature for more than 50 main belt asteroids belonging to different taxonomic classes shows that the variation of the polarization degree Pr as a function of wavelength is generally well described by a linear trend. It typically does not exceed 0.2% in the studied spectral range 0.37-0.83 microns and tends to increase for increasing phase angle. Asteroids belonging to the S and M classes are found to exhibit a deeper negative branch and smaller positive polarization for increasing wavelength (negative sign of the slope of ΔPr/Δλ). Since the objects belonging to these classes are known to exhibit reddish reflectance spectra, the observed wavelength behavior of negative polarization contradicts the well-known inverse correlation of Pmin and albedo. Low albedo asteroids show larger dispersion of spectral slopes, but the overall trend is characterized by a shallower negative branch and a larger positive polarization for increasing wavelength (positive sign of the slope of ΔPr/Δλ). A few exceptions from this general trend are discussed. The observed variety in the wavelength dependence of asteroid polarization seems to be mainly attributed to surface composition. 相似文献
94.
Pavlo P. Korsun Irina V. Kulyk Oleksandra V. Ivanova Viktor L. Afanasiev Francois Kugel Claudine Rinner Yuriy M. Ivashchenko 《Icarus》2010,210(2):916-929
We present the study of dust environment of dynamically new Comet C/2003 WT42 (LINEAR) based on spectroscopic and photometric observations. The comet was observed before and after the perihelion passage at heliocentric distances from 5.2 to 9.5 AU. Although the comet moved beyond the zone where water ice sublimation could be significant, its bright coma and extended dust tail evidenced the high level of physical activity. Afρ values exceeded 3000 cm likely reaching its maximum before the perihelion passage. At the same time, the spectrum of the comet did not reveal molecular emission features above the reflected continuum. Reddening of the continuum derived from the cometary spectrum is nonlinear along the dispersion with the steeper slop in the blue region. The pair of the blue and red continuum images was analyzed to estimate a color of the comet. The mean normalized reflectivity gradient derived from the innermost part of the cometary coma equals to 8% per 1000 Å that is typical for Oort cloud objects. However, the color map shows that the reddening of the cometary dust varies over the coma increasing to 15% per 1000 Å along the tail axis. The photometric images were fitted with a Monte Carlo model to construct the theoretical brightness distribution of the cometary coma and tail and to investigate the development of the cometary activity along the orbit. As the dust particles of distant comets are expected to be icy, we propose here the model, which describes the tail formation taking into account sublimation of grains along their orbits. The chemical composition and structure of these particles are assumed to correspond with Greenberg’s interstellar dust model of comet dust. All images were fitted with the close values of the model parameters. According to the results of the modeling, the physical activity of the comet is mainly determined by two active areas with outflows into the wide cones. The obliquity of the rotation axis of the nucleus equals to 20° relative to the comet’s orbital plane. The grains occupying the coma and tail are rather large amounting to 1 mm in size, with the exponential size distribution of a−4.5. The outflow velocities of the dust particles vary from a few centimeters to tens of meters per second depending on their sizes. Our observations and the model findings evidence that the activity of the nucleus decreased sharply to a low-level phase at the end of April–beginning of May 2007. About 190 days later, in the first half of November 2007 the nucleus stopped any activity, however, the remnant tail did not disappear for more than 1.5 years at least. 相似文献
95.
Trudy Doelman Robin Torrence Vladimir Popov Mihail Ionescu Nickolay Kluyev Igor Sleptsov Irina Pantyukhina Peter White Mark Clements 《Geoarchaeology》2008,23(2):243-273
Artifacts made from volcanic glass have been found in archaeological contexts dating from the Late Palaeolithic (ca. 20,000 yr B.P.) through to the end of the Bronze Age (ca. 2700 yr B.P.) in the southern Primorye region of Far East Russia. A geoarchaeological survey of volcanic glass outcrops assessed the various potential sources to determine their potential for sustained exploitation. A characterization study of source samples and artifacts from 27 spatially and temporally dispersed sites using a combination of PIXE‐PIGME and relative density identified which sources had actually been exploited and a technological analysis of the assemblages described patterns of use. The combination of these three approaches shows the impact of a relatively stable geological environment on patterns of procurement and exchange. © 2008 Wiley Periodicals, Inc. 相似文献
96.
Irina Shtangeeva Antti Vuorinen Bernd Rietz Liisa Carlson 《Geostandards and Geoanalytical Research》2001,25(2-3):299-306
A detailed characterisation was carried out for soil sampled from sites with different levels of contamination before and after the cultivation of oats and barley. Mineralogical composition, concentration of exchangeable cations, dynamics of soil pH and acid neutralisation buffer capacity of the soil were studied. A total of 21 elements in the soil and 28 elements in the plants were determined by instrumental neutron activation analysis. Distribution of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn and Pb in soil leachates was studied by sequential leaching procedure and ICP-AES. It was found that plants significantly affect most of the soil characteristics including the leaching of heavy metals. 相似文献
97.
Irina Tupikova Michael Soffel Sergei Klioner 《Celestial Mechanics and Dynamical Astronomy》1999,74(3):147-152
Starting from the classical expansion of the perturbing function in the three‐body problem, the transformation to individual
orbital elements is performed in principle up to any degree in small parameters. Some corrections to the results presented
in the well‐known article by Yuasa on secular perturbations of asteroids are given. Consequences for the expansion of the
indirect part of the perturbing function are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
98.
Strujkov Sergey F. Chizhova Irina A. Konstantinov Michael M. 《Natural Resources Research》1999,8(4):315-343
The Okhotsk–Chuckchee volcanic belt (OCVB) represents a world class gold–silver province, being a well-studied part of the Circum-Pacific Rim. Extensive research, preceding the system compilation, included collection of various data on major gold–silver, silver–lead–zinc, and tin–silver ore fields (with some data on minor gold–quartz, gold–sulfide, and gold–rare-metal sites). The database consists of 129 ore fields of the OCVB and comprises 433 geological, mineralogical, geochemical, and geophysical indicators. Using the original pattern recognition programs (accounting the frequencies and correlation of the indicators), the most informative indicators were selected, their weights (both positive and negative) were identified, and an expert system (solution tree) was compiled. The computer system is intended to be an assistance to an expert in the ore field potential evaluation. The system includes several blocks of questions with a goal of classifying the geochemical type and size of the analyzed ore field. The questions have an indirect character, so they could be answered by an expert at early stages of exploration (before drilling). The level of recognition of sizes of the ore sites in the control populations is 95% or higher. The aim of the expert system is to reestimate a large number of known ore sites in a relatively brief period of time with the aid of the personal computer. The revealed patterns could be used in other less studied parts of the Circum-Pacific belt. 相似文献
99.
Radon Distribution in Domestic Water of Texas 总被引:1,自引:0,他引:1
Irina Cech Charles Kreitler Howard Prichard Alfonso Holguin Mengistu Lemma 《Ground water》1988,26(5):561-569
100.
Nonconventional hydrocarbon targets in the crystalline basement, and the problem of the recent replenishment of hydrocarbon reserves 总被引:1,自引:0,他引:1
Analysis of the distribution of oil pools in sedimentary cover has shown that known platform hydrocarbon fields are closely associated with faults in the crystalline basement and the sedimentary cover itself. Oil pools in the lower productive beds of the sedimentary cover are linked to faulted zones in the crystalline basement. A genetic relationship between oil fields and tectonic dislocations indicates a dominant role for vertical migration in the accumulation of commercial hydrocarbons in the Paleozoic. The conducted geochemical, palynological, geophysical and geological studies have shown that oil and gas pools in the upper sedimentary cover have been formed due to the vertical migration of hydrocarbons, which is also confirmed by the vertical alignment of the oil pools. 相似文献